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feat(library/compiler/llnf): eliminate cases term where all reachable branches are equal

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This commit is contained in:
Leonardo de Moura 2018-10-29 14:57:37 -07:00
parent 91b59a2f12
commit 998293b8ca
1 changed files with 19 additions and 3 deletions
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22
src/library/compiler/llnf.cpp
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@ -392,7 +392,9 @@ class to_llnf_fn {
@decidable.cases_on t _cnstr.0.0 _cnstr.1.0
```
which reduces to `t`. */
bool is_id = true;
bool is_id = true;
/* We use `all_eq` to track whether all reachable cases are equal or not. */
bool all_eq = true;
/* Process minor premises */
for (unsigned i = 0; i < cnames.size(); i++) {
unsigned saved_fvars_size = m_fvars.size();
@ -421,26 +423,40 @@ class to_llnf_fn {
minor = instantiate_rev(minor, fields.size(), fields.data());
minor = visit(minor);
if (!is_enf_unreachable(minor)) {
num_reachable++;
/* If `minor` is not the constructor `i`, then this "cases_on" application is not the identity. */
unsigned cidx, ssz;
if (!(is_llnf_cnstr(minor, cidx, ssz) && cidx == i && ssz == 0)) {
is_id = false;
}
minor = mk_let(saved_fvars_size, minor);
if (num_reachable > 0 && minor != some_reachable) {
all_eq = false;
}
some_reachable = minor;
args[i+1] = minor;
num_reachable++;
} else {
args[i+1] = minor;
}
}
/* TODO(Leo): check whether all reachable cases are equal or not. */
if (num_reachable == 0) {
return mk_enf_unreachable();
} else if (is_id) {
return major;
} else if (num_reachable == 1) {
return some_reachable;
} else if (all_eq) {
expr r = some_reachable;
/* Flat `r` if it is a let-declaration */
buffer<expr> fvars;
while (is_let(r)) {
expr val = instantiate_rev(let_value(r), fvars.size(), fvars.data());
expr fvar = m_lctx.mk_local_decl(ngen(), let_name(r), let_type(r), val);
fvars.push_back(fvar);
m_fvars.push_back(fvar);
r = let_body(r);
}
return instantiate_rev(r, fvars.size(), fvars.data());
} else {
return mk_app(fn, args);
}